....Was this right or wrong...?

My friend called me over to her house bc she said she found a weird plant growin in her brothers window..I immediately thought it was marijuana and she said she did too but wasnt sure thats why she asked me...we googled it because it didnt have any smell and it was still small but we found out it was and so we put it in a bag(the pot and all) and threw it in a dumpster. Could we get in trouble for trying to get rid of it? We had nothing to do with it she just didnt want her brother to be smoking marijuana or it be in her house..hes 18 but thats still illegal right? And we told her mom when she got home and she said she would talk to him about it. Was it bad for us to get rid of it? Im sooooooooooo confused D: